A worldwide study led by Keele University has shown that people who sleep for more than eight hours each night are at a greater risk of mortality and cardiovascular disease than people who sleep for seven hours or less.
The study also showed that sleeping for ten hours is associated with a 30% increased risk of dying, compared with sleeping for seven hours.
As reported in the Journal of the American Heart Association, lead author Chung Shing Kwok and colleagues studied the link between self-reported sleep duration and quality, cardiovascular outcomes and mortality across 74 studies including more than 3 million people.
“This research began because we were interested to know if it was more harmful to sleep below or beyond the recommended sleep duration of seven to eight hours. We further wanted to know how incremental deviation from recommended sleep duration altered risk of mortality and cardiovascular risk,” says Kwok.
The study also found that sleeping for ten hours increases the risk of death from stroke by 56% and the risk of death from cardiovascular disease by 49%.
Kwok says the findings have important implications for the public because they show that too much sleep can increase cardiovascular risk. They also have important clinical implications because they suggest that doctors should ask more about sleep duration and quality when talking to patients.
If excessive sleep patterns are found, particularly prolonged durations of eight hours or more, then clinicians should consider screening for adverse cardiovascular risk factors and obstructive sleep apnea, which is a serious sleep disorder that occurs when a person's breathing is interrupted during sleep,”
Chung Shing Kwok, Keele University
The results are evidence that sleeping for longer than the recommended seven or eight hours could be linked to a moderate degree of physical damage, compared with sleeping for fewer hours.
“The important message is that abnormal sleep is a marker of elevated cardiovascular risk and greater consideration should be given in exploring both duration and sleep quality during patient consultations,” concludes Kwok.